Placental development is a complex process that involves interactions among multiple cell types and may be affected by maternal nutrition during pregnancy. Further, the fetal origins of adult disease hypothesis posits that maternal nutrition during pregnancy has consequences for the future adult health ofthe fetus. In particular, it has been shown that severe caloric restriction during early pregnancy results in increased risk of obesity and cardiovascular disease when the affected fetus reaches middle age. The mechanisms by which this occurs are poorly understood, but the timing suggests that altered placental development may be involved. The hypothesis underlying this proposal is that the hormone leptin influences multiple steps in the process of placental development. Leptin is produced by fat cells, and thus is a potential mediator ofthe effects of nutrition on placental development and subsequent adult health. The first specific aim is to determine whether leptin shortage mediates effects of nutrition on fetal and placental programming. Animals will be placed on a restricted diet with or without leptin replacement, and effects on placental development and adult adiposity determined. Placental size, morphology, gene expression, and gene methylation will be examined. In addition, the offspring of treated mothers will be followed through adulthood to determine longterm effects of diet and leptin replacement on obesity and lipid profiles. The second specific aim is to determine effects of leptin on placental differentiation at the cellular level. Trophoblast stem cells will be used to study the role of leptin in the differentiation of giant cell, syncytiotrophoblast cell, and spongiotrophoblast cell types. In addition to the scientific aims ofthe proposal, a goal of this "Pathways to Independence" project is to establish an independent laboratory in reproductive biology to pursue research on the effects of maternal environment on placental development.